Plant for the production and heating of compressed air



Aug. 9, 1949. R. RUEGG 7. 2,478,504

PLANT FOR THE PRODUCTION AND HEATING OF COMPRESSED AIR Filed Feb. 12, 1946 Fig.1

Inu entor by M4.

Auo rnegs Patented Aug. 9, 1949 PLANT FOR THE PRODUCTION AND HEATING OF COMPRESSED AIR Rudolf Ruegg, Zurich, Switzerland, assignor to Aktiengesellschai't Fuer Technische Studien, Zurich, Switzerland, a corporation of Switzerland Application February 12, 1946, Serial No. 647,052

In Switzerland February 22, 1945 2 Claims.

This invention relates to a plant for the production of compressed air, e. g. blast furnace air, in which air is brought in at least one compressor to a higher pressure than the pressure required in the compressed'air consumer, then heated in a heater by a supply of heat derived from an external source, and afterwards expanded (whilst giving up energy) in at least one turbine which drives the compressor.

In such Plants if it is at all possible, an operation without supply of external power is aimed at, that is to say endeavour is made to produce in the turbine just so much energy as the compressor requires. It is however important that even under altered working conditions, e. g. partial loads, an operation without supply of external power shall be still ensured. In order to attain this, it is already known to adapt the consumption of energy by the compressor to the particular working conditions of the moment by varying the degree of intermediate cooling during the process of compression, or to vary the amount of air compressed in the compressor to the final pressure or the amount of air expanded in the turbine to the final pressure.

The object of the present invention is to provide further means which will render an operation without supply of external work possible under difierent working conditions, and this in a manner involving a small consumption of heat and allowing of a rapid adaptation to the working conditions at any particular moment. For this purpose according to the present invention, a quantity of air which is greater than the quantity required by the compressed air consumer is withdrawn from the turbine at least before the last stage thereof and passed again into the heater. The part which is to be passed to the consumer is then branched off from this quantity of air heated for the second time, and the remainder together with the quantity which has not been passed for the second time through the heater, expanded still further in the turbine, after which this remainder serves, at least in part, as air to support combustion in the heater. v

Two simplified constructional forms of the subject matter of the invention are shown in the accompanying drawing in which:

Fig. 1 represents a plant for the production and heating of blast furnace air, in which the compression of the air takes place without intermediate cooling and Fig. 2 represents a plant for the production of blast furnace air in which the air is intermediately cooled once during the compression 2 thereof, and in which also a part of the fuel is introduced into a combustion chamber placed between two systems of pipes.

In Fig. 1 of the drawing I denotes a'blast furnace. The compressed air required in this latter is supplied by a compressor 2, whichdraws air in from the atmosphere. This compressor 2 not only draws in the quantity of air required in the blast furnace l but also the additional quantity which it requires to be able to drive the compressor 2 in the way to be hereinafter described.

'The compressor 2 compresses the whole of the quantity of air drawn, in to a pressure which is higher than that which corresponds to the consumption pressure at the blast furnace i increased by the normal additional losses of pressure in the pipes and apparatus. The compressor 2 forces the compressed air through a pipe 2 into a system of pipes 3, which, for the greater part, are accommodated in a second flue 5 of a heater 4. This system of pipes 3 is traversed by the air to be heated from below upwards, i. e. in the opposite direction to that in which the flue gases pass. The air heated therein passes through a pipe 6 into the high pressure part i of a two casing turbine the low pressure part of which is denoted by 8. In the high pressure part i of the turbine the air expands, giving up energy, as it does so, to the compressor 2 and after having passed through all the stages of this part I it passes into a pipe 9 which is connected to a second system of pipes iii of the heater d. This system of pipes Ii! is accommodated in a first flue ii of the heater 5 and the air therein which is to be heated flows through them likewise from the bottom upwards, but in the same direction as the heating gases. The air heated for the second time in the system of tubes 50 passes into a pipe it, which is connected to the inlet to the low pressure part 8 of the turbine. At the point I! on the pipe it the quantity of compressed air required in the blast furnace i is branched 05' from the current of air which has been heated for the second time. The remainder of this current of'air is expanded still further in the low pressure part 8 of the turbine giving up energy as it does so to the compressor 2 and passes finally through the pipe l3 into the burner Id of the heater 4 there to serve as air for the support of combustion. l5 denotes the combustion chamber of the heater. From the pipe 9 there branches ofl. a by-pass pipe l6, which is connected to the pipe II and in which an adjustable regulating device I! is inserted. A quantity of the airexpended in the high pressure part I of the turbine 'sure section of the turbine 21.

and adjustable at any time, can pass over directly into the low pressure part 8 of the turbine without going through the system of tubes I0. With the help of the quantity of air passing through the pipe IS the temperature at the inlet to the low pressure part 8' can be controlled. This enables firstly the energy produced in the low pressure part 8 to be controlled and secondly it a higher temperature is desired for the air to be supplied to the blast furnace, correspondingly highly heated air can be prevented from passing into the low pressure part 8, it being always possible to allow such a quantity of colder air to pass through the pipe l6 into the pipe I I that the air passing into the low pressure part 8 shall have approximately the temperature for which this part is designed. For the sake of completeness it should also be stated that 18 denotes a preheater for the fuel which flows to the burner 14 through a pipe I9. 20 is an auxiliary motor, which serves to start up the plant.

The constructional form shown in Fig. 2 differs in the main from that just described only by the fact that the compressor 2| in which the whole of the quantity of air drawn in is compressed, is built with two casings and that the air is cooled intermediately during the process of compression in a cooler 22. In consequence of the provision of a short-circuit pipe 23 with a regulating device 24 the quantity of air which is subjected to intermediate cooling, can be regulated and therefore also the energy absorbed by the compressor 2|. In other respects the second constructional form of the plant diflers from the one previously described also by the fact that a further combustion chamber 29 is provided between the system of pipes 25 in which the whole of the quantity of air drawn in is heated, and the system of pipes 26 in which at least part of the airexpanded in the high pressure stages .of the turbine 21 is heated for the second time.

The quantity of air required in the blast furnace 32 is likewise branched off from the quantity of air heated for the second time in the system of pipes 26 at the point on the pipe 3|, which leads from the system of pipes 26 to the low pres- The remainder of this quantity of air is expanded still further in said low pressure, section of the turbine 21 giving up, as it does so, energy to the compressor 2|. The air escaping from the turbine 21 is supplied through pipes 40, 4|, 42 as air to support combustion to the burners 33 and 34 of the heater 35. A short-circuit pipe 36 with an adjustable regulating device 31 permits of an adjustable quantity of the air escaping from the high pressure part of the turbine 21 into pipe 38 to pass directly into the pipe 3! without passing through the system of pipes 26, so that any desired temperature may be adjusted at the inlet to the low pressure section of the turbine 21. According to the adjustment therefore of theregulating device 31 the whole or only a portion of the air expanded in the high pressurepart of the turbine 21 flows through the system of pipes 26 in which air is heated for the second time.

The air escaping from the low pressure part of the turbine need not be wholly used as air for the support of combustion. Part ofitimay be used for preheating purposes for example.

The above described possibility of being able to influence the temperature of a quantity, of

air withdrawn from the turbine and heated a second time in the heater prior to its entry into the turbine again so as to regulate the energy supplied by the compressor, can be used simultaneously with one or more other means for influencing the amount of energy consumed by the compressor or produced by the turbine. Such further known means are for example varying the amount of air serving as an excess in the heater, and varying the amount of air compressed in the compressor to the final pressure or that expanded in the turbine to the final pressure.

What is claimed is:

1. A plant for compressing and heating air and delivering the heated compressed air at a desired rate at desired temperature and pressure, comprising in combination at least one compressor arranged to draw air from the atmosphere at a rate greater than said desired rate and compress it to a pressure greater than said desired pressure; a heater structure enclosing a combustion space and an ofitake passage leading therefrom; combustion means in said space;

All

a primary heat exchanger and a secondary heat exchanger mounted in said ofltake passage so as to derive heat from products of combustion flowing therethrough from said combustion means; a staged turbine connected to drive said compressor and subdivided into two units in the first of which air can be expanded from the pressure to which it is compressed by the compressor approximately to said desired pressure and in the second of which air can be expanded from said desired pressure to a pressure suited to said combustion means; connections for leading air from the compressor outlet to the inlet of the primary exchanger and from the outlet of said exchanger'to the inlet of the first turbine unit; connections from the outlet of the first turbine to the inlet of the secondary heat exchanger and from the outlet of said exchanger to the inlet of the second turbine unit; a final discharge connection for heated compressed air leading from the outlet of said secondary ex- I changer; a connection from the outlet of the second turbine unit to said combustion means; a flow connection from the outlet of the first turbine unit to the inlet of the second turbine unit; and a regulating device controlling flow through the last named connection.

2. The combination defined in claim 1 in which the compressor comprises two staged units connected in series with an interposed intercooler; and means are provided to regulate the cooling action of said intercooler.

RUDOLF RUEGG.

REFERENCES orrnn The following'references are of record in the file of this patent:

UNITED STATES P ATENTS Certificate of Correction Petent No. 2,478,504 August 9, 1949 RUDOLF RUEGG It is hereby certified that error appears in the printed specification of the above er/f numbered patent requiring correction as follows:

Column 4, line 39, claim 1, after the word turbine insert unit; and that the said Letters Patent should. be read with this correction therein that the vsame may conform to the record of the case in the Patent'Oflice.

Signed and sealed wig-1 3 h day of December, A. D. 1949';

THOMAS F. MURPHY,

Assistant Oommiasioner of Patents. 

